This program project is studying the effects of lead at doses less than those associated with clinical symptoms on the development of school age children and experimental organisms. Lead burden is measured in childred in the first two grades, and neuropsychologic function is measured in high and low exposure groups. The relationship of confounding covariates to outcome is controlled in the analysis. Transport of aminoacids into the brain, synaptogenesis and dentritic complexity is being studied in the rabbit and rodent at controlled doses of lead lower than those which produce frank encephalopathy.